Telephone system and apparatus.



c. L. GOODRUM TELEPHONE SYSTEM AND APPARATUS.

Eatented Apr. 13,1915.

9 SHEETS-SHEET 1.

APPLICATION FILED APR. I, IIJOS.

C. L. GOODRUM.

TELEPHONE SYSTEM AND APPARATUS. APPLICATION man APR. 1, 1905'.

Patented. Apr. 13, 1915.

9 SHEETS-SHEET 2.v

l'V/TNESS/ES v c. LQGOODRUM. TELEPHONE SYSTEM AND APPARATUS.

APPLICATION FILED APR. i. I905.

Patentd Apr. 13, 1915.

WHIICBSZQ i Patented Apr. 13, 1915.

9 SHEETS-SHEET 4.

APPLICATION FILED APR.1, 1905 'wllmeseee C. L. GIOODRUM. TELEPHONE SYSTEM AND APPARATUS. APPLICATION FfLED APR. h 1905.

1,1,35,01 1. ;*at ntea Apr-13,1915.

9 SHEETS SHI-JET 5.

witnesses c. LLGOODRUM.

TELEPHONE SYSTEM AND APPARATUS.

APPLICATlON FILED APR. 1. 1905. y Patented Apr. 13, 1915:

9 SHEETS-SHEET 6.

Witnesses C. L. GOODRUM. TELEPHONE SYSTEM AND APPARAIUS.

' i v APPLICATION FILED APRL 'I I905- 1,135,011. Patented Apr. 13, 1915..

EC.L.GOODRUM! TELEPHONE SYSTEM AND APPARAIUS,

I APPLICATION FILED APR. 1, 1905. 1,135,01 1. Patented Apr 13, 1915.

9 SHEETS SHBET 8.

x W V attorney c, L. eoo'unum TELEPHONE SYSTEM AND APPARATUS. AP PLICATION HLED APR. 1, I905.

Patented Api. 1f3,1915'.

k a sums-SHEET 9.

TE s ;ATENT QFFICE.

CHARLES LANE GOODRUM, OF RooHEs'rEa, NEW vvo K, ASSIGNOR, BY 'MEsNnAssIGN- N. .Y., A CORPORATION or ILLINOIS.

i MENTS, TO WESTERN ELECTRIC COMPANY, OF CHICAGO, ILLINOIS,:AND YORK,

TELEPHONE SYSTEM AND APPARATUS.

To all whom it mag concern:

Be it. known that I, OIIAnLEs Lass Goon- RUM, a citizen of the United States, residing atRochester, in the county of Monroe and State of New York, have invented certain new and-useful, Improvements in Telefor putting the lines in connection with idle in important after.

plio'ne Systems and Apparatus, of which the following is a specification, reference being had therein to the accompanying drawing. My invention relates to telephone systems,

and particularly to automatic exchange sys teins.

It has for its object the provision of improved circuits and apparatus for such systems, the simplification of both the switches and the circuits, the use of common battery, the use of party-lines, and in generalimprovement in all the various features Whichhave heretofore been used in automatic systems.

' The'leading. characteristic feature of my invention consists in the provision of a number of connecting switches or other means less than the total number of lines to be served thereby, for purposes of selection;

and. the provision of a switching means.

identified with each line whereby the same may become identifiedand connected incalling with suitable selecting and connecting apparatus. This latter is, divided into groups, by means of which success ve selections are made; and another feature of my invention is that .these groups do not bear a decimal relation to each other of necessity, but maybe and are preferably arranged in what may be called semrdecnnal relation,

.five as a multiple being substituted for 10.

In an exchan e of a thousand subscribers I employ what I designate as B," C and switches for selecting; and A" switches Specification of Letters Patent. Patented Apr, 13,1915, Application filedApril 1, 1905. Serial No. 253,227. I

its arms more each in a constant plane, being fed forwardly by what are called group steps, and preferably backward by individual steps to select the proper unit in a group. The switches are mounted entire on a fiat base for each one, the bank contacts being made removable without complication, so that all the operative parts of each switch are removable for inspection and repairs. By my arrangement I also economize space and protect the switches from dust; for each switch basewith the parts carried on it is treated like a drawer unit in a cabinet,.all

cable and wiring being disposed on the back of the cabinet (or rack) and all the work; 1ng parts'being removable from the front.

Referring to the drawings, Figure 1. is a.

top plan view of a B switch. Figs. 2., 3, 4'

and 5 are details thereof. Fig. 6 is a top plan view of an A switch. Fig. 7 is a vertical section thereof looking from the left. Fig. 8 is a detail of the contactb'anks of the A switch. Fig. 9 is a top plan view of the G switch, and Fig. 10 is a detail View of its banks. Figs. 11, 12, 13 and 14 are continuing diagrams showing respectively the circuits ofthe A, B, C and G switches- Fig. 15 shows a called subscribers suit and his A switch when idle.

The mechanical structure of the C switch is substantially the same as that of the ]3 switch, so I have not complicated the presline cirentation of the case by introducing a' C- switch drawing, which would be almost a precise duplicate of'Fig. 1.

I will first briefly outline the functions performed by the successive switching operations, so as to enable an intelligent grasp to be taken of the apparatus and circuits as subsequently described. I-will then pass to some description of the mechanical structures; and thereafter will, advert to some peculiarities of the circuits. Finally I will give a statement of operation which willv convey the clearest idea of my system as a whole, and will point out the noveltythereof in my claims.

According to will be observed that its'bank there are the present scheme, 1 pro-i vide each subscribers line with what I call twelve contacts per row. That is to say there are twelve trunks, or twelve Bswitches which each line may reach, and I find that the percentage of B switches required in a city exchange is commonly five per cent, rarely exceeds ten per cent, and almost never exceedstwelve per cent.

lVhen a subscriber calls his A switch startsand instantly connects him with an idle B switch. he B switch, and it the exchange exceed one thousand in size the C switch, are controlled by impulses over the vertical side of line to select a group of trunks to subsequent switches, and then to select anidle trunk in the group. This brings the circuit to the G switch, which is then in its turn controlled to select the wanted subscribers line, the same being performed by merely stepping the armaround over a single set of contacts. When the wanted line is selected the condition of the switch relays is such as to leave the ringing generator on the line for a short period, then oil? for an interval, then on again, and so forth until the called. subscriber answers or the calling subscriber abandons the call and hangs up. Upon so hanging up the switches are all restored by restoring magnets working back one upon another through the trunks; whereas if the called subscriber answers his line takes current,his A switch is cut ,oil', the ringing relay is cut off, bridging battery is cut back to the calling subscriber giving talking can rent for his transmitter, which he did not have before. In the present case, instead of employing the double motion switches commonly known as the Strowger switches the same having been, improved by Messrs. Lundquist, Ericsson and others, I have adopted a very different design. In the first place, myswitches are all mounted upon flat bases, so they can be mounted like drawers in a cabinet; and in the second place I make them separable, one part carrying the contact banks and multiple wiring connec-' tions, and the other part carrying the relays and the working magnets together with the switch arms or wipers. These second parts are provided with contact terminals which when the parts are in position regisfor with corresponding terminals on the first parts, completing the connections of the relays, etc. These second parts are removable and all of the same kind are interchangeable, and as it is with these parts that a very large percentage of the troubles occur, it'is obvious that I have achieved an important end by this arrangement; for in case of any trouble with the working parts --of a switch of any letter, it is only necessary to slide out the defective switch body and slidein another in its place.

I have chosen to depart from the decimal system of trunking because thereby 1 can These terminals It are used to complete the point to receive the coned end of the spindle .are mounted the ratchet simplify the switches and get. better results. In the ordinary Strowger switch it. customary at each completion of a link or trunk to step up the switch arm to the row of contacts desired, and then connect a socalled rotary relay which would carry the wiper around continu usly until it rests upon an idle contact. in the present case I provide fifty contacts in the switch (1' reterparticularly to the Band C switches) ad divided into groups of'five. Each group of live small contacts is-equal in angular dimension and is overlaid'by a single broad contact. Each switch has a double ratchet motion; a pawl Working into a coarse ratchet first steps the Wipers aroun'clto the group contact desired, clearing five of the small contacts at a junip;th.en a scape pawl working into a finer ratchet (live to one of the other) steps back the Wipers one step at a time in the group thus selected until the desired unit contact is reached. Thus in these switches I only give five trunks to a switch, and I can multiply thenumber of switches if required.

in addition to the above features of novelty I provide in connection with the present system a registering scheme which enables the time of callsv to he recorded. Many :teatures of novelty will appear from the de- .scription and statement of operation.

Referring now to Fig. l E is a base plate of metal rectangular in shape and divided along the line 8 at its upper end, leaving an upper rim 6 to form abase for the con-- act banks F. Upon this base a row of socket contacts H are mounted in insulation, with which cooperate the contact tQIIHl nals is mounted in a strip on the base circuits from the cable in the racks to the magnetsshown on the base E.

The contact hanks F are formed as an arc of a circle somewhat less than and concentric with the center or axis Z) of the switch spindle. In the banks are the broad contacts 48, and the individual trunk con tacts m, which will be pointed out here after in referring to the diagrams. Extending across the upper end of the plate E is a bridge 6 drilled at its middle spindle Z Directly in line with the c g in the bridge a similar opening is formed n the plate for-the other endot' the spii in a box secured around the foot end or this spindle is the coiled spring Z)" which serves toreturn the spindle to initial position when released as hereinafter described. Jpon the Wheels 5' wheel 5 and the Wipers Z), 25 5 5 5 These may be and preferably are insulated, particularly the Wipers, each Wiper has an are 6 extendin around the spindle, and upon and b the stop ratchet which serve as collector ringsor i'segments,

rest the ends of contact springs I) carried in insulation onthe right-hand side of the bridge 6 as shown in Fig. 1, each spring having a tail b for the attachment of its circuit wire, and an extension 6 which recelves the wiper when turned all the way around to clear it from the bank contacts and hold it in proper position for reengage ment therewith, this clearing being necessary when the plate E and its attached parts are removed from the bank. To facilitate the removal and replacing of the platein proper alinement withthe base 6 of the banks, I provide a pair of guide tongues e? attached to the plate e and overlying the plate E when-in position. The bank as a wholeis carried on four posts 72 best shown in Figs. 3 and 5, and each bank of contacts plates 7 secured by the wheel 6 is the pawl 6 on a dog 5 pivtending to throw gaging the teeth 7). Cooperating with this ratchet to form an escapenient, is the armaoted in a yoke attached to the'base plate E as shown in Figs. 1,2 and 3. The dog has a joint inthe middle, and a spring normally it up with the ratchet ens ture lever 19 of the magnet M tt-his lever having a chisel-edge to enter the teetlnand a bar b to withdraw the pawl as the ed? enters, by forcing up the tail 6 of the do Opposite the ratchet the dog has a toe'b with which cooperates a hook onthe end of the spring 5 carried on the end of the armature lever of the release magnet M lVhen this armature is attracted, the pawl I) being up, the spring reaches up, the hook takes dog, perhold ofthe toe and pulls down the mitting the spring 6 to return the spindle b and all its wipers to zero position as shown inFig.1-.

In order to step'the wheel 71*- around, the magnet. M carries apawl b pivoted-at b and having an angle stop Z) coming against a fixed stop 6 magnet is deenergized as shown in Fig. 1. As the magnet M is energized, its vertical lever is thrown to theleft, a projection on the lower "part thereof comes against the spring 6 to remove it from-the toe b and permit the retaining pawl to rise into-engagement with the teeth'b, the stop I) at the same time leaves the fixed-stop 6 the spring 6" swings the pawl 6". around. the

pivot 6 until its point engages the teeth on the ratchet wheel- 65, each tooth on -this- Wheel moving the arms around over fivecontacts m at a jump, while each tooth '6 moves the" arms over one contactsingly. As the pawl bpushes the wheel' b on the bridge e when the.

around,"

theme-l3" on the upper end of'thearm'ature lever comes over in the path of andv serves as a stop forthe teeth on a secondwhee'l 72 furnishing a.

in'the rotation. Each arm has an annular positive stop f each p collector ring 6. as stated upon which rests the spring 6 When it is desired to remove the switch body from the rack,the arms are turned all the wavaround until they rest on the fixed contacts b, and come away with the body plate'E.

Further description of the B and C switches is unnecessary in view ofthe statement of operation hereafter, and the fullness of the illustration. It is to be under-' stood that I intend to claim everything I have shown, as my own invention.

- Referring now to Figs. 6 and'7, and also Figs. 8, 9 and 10 I will point out briefly the distinctive features of the A and G switches respectively. shown therein. The only difference between these switches-in essentials is in the number of relays they carry. Each of them; has the same kind of a baseplate E asthat already described. Each has a similar bridge e and each has its own spindlea or g and arms a, g eto.;- In Fig. 6 it will be observed the detent action of the pawls is i different however, and there is but a single ratchet wheel on the'spindle. The mechani cal features here being identical in both.

switches, a single description will suflice,"

- tended from a pivot beyond which it has a In Fig. 6 the magnet M carries*on'itsa1-- mature a' release spring a, with a hookon the end adaptedto reach up when the armature is attracted and engage a pawl carried by and pivoted on the armature lever of the tail turned down likea'bell crank and under lying a-leaf'spring on the armature levef. and 'the' first motion releases the drop member from the spring tip a. The leaf spring immediately throwsthe pawl up into engagement with the teeth ofthe ratchet wheel. A retaining pawl'a is pivoted on a bracket on the frame and when the actuating pawl rises it permit-sthis to rise also under the influence of a spring a and when'the actuating pawl is pulled down'by the hook spring-e 3, it also pulls the retaining pawl a" .downwith it. These two switches,,QA flndIG," l13,-Ve ten contacts cent. of connective apparatus is required, and twelve if twelve per cent. There is no necessity for a double movement; there is onlya single actuating magnet, ,M? or M.

and; a release magnet M "or: M. The'arrangement' of the switch base, E, 'and the frame carrying the bank contacts, as well-as each if; ten per the sliding contact spring connections be-- tween the two, is the same as in the switch. r

- jr he relays. I- ainrey at "witll one excef end of the core. On one arm of this magnet issecured a leaf spring having its end bent up and resting upon the raised middle portion of the armature over the knife edge, so as to hold the armature in position. Along theother arm of the magnet I secure a corn tact spring forming one side of the circuit to be controlled, the armature forming the other. I

The magnets M M M hi have contacts in addition to being working magnets.

, In each case the contacts are secured to the frame of the magnet and are actuated bya bell crank lever, one end of which is the armature.

Referring now to the circuits, it will be observed that I have shown at the subscribefs station what is known as Strow ger apparatus, the essential. parts thereof comprising the dial and receiver hook with the contacts controlled by each being arranged and operated as in the standard apparatus of-th'is type. That is, the receiver hook is adapted when released to put the first of all transmitter and receiver across the linethrough the induction coil, to render the dial operative, and when depressed the hook opens said bridge and in its downward movement momentarily closes both sides of the line to ground to effect the release of the switches. T he dial when thus rendered operative is adapted when actuated to open the bridge of the subscribers instrument and in its retrograde movement to ground the vertical side of the line one or more times to transmit a corresponding number of current impulses thereover and upon returning to its normal position to momentarily ground the rotary side of the line to despatch a single impulse of current thereover and finally, in arriving at its normal POSliZlOI1,'li3 closes the bridge. The series of impulses sent over the vertical side of the lineeifects the operation of one or another of the switches and the single impulse sent over the rotary side, called the confirming impulse, cuts the lines through from one switch to-the next switch, 2'. 6., it renders a switch.inoperative when it has performed its function and renders another switch in readiness to be operated. The sub-station circuits of the Strowger apparatus needs no description for those skilled in the art and it should be understood i can substitute meson comprises two push buttons .which may be employed for performing the functions at tributed to the dial above referred to, each arranged to connect one side of the line to ground when actuated.

The subscriber s instrument circuit described more specifically and illustrated in Figs. 1.1 and 15, comprises a transmitter T, a receiver R and induction. coils I, a switch hook H, ringer Q, and condenser C. The receiver R is shown in a local circuit 21G terminating in one winding of the induction coil 1. The transmitter circuit may be traced as follows: (assumthe instrument circuit to be closed by removing the receiver) (Fig. 11) from. the vertical side of the line 1 by branch 30, wire 250, springs a a, wire 2-10, springs a a line winding of induction coil ii, transmitter T, wire 220, springs a a wire 40, rotary side of line 2. Additional spring contacts a a and a a a and a, are the ones operated by the dial (not shown) and a a a a and (1 are the contacts controlled by the receiver hook 4:.

The subscribers switch. In starting a call the first impulses come in after the A switch has selected an idle trunk through its wipers a and a, and put the line-thereon, and thence to a B switch, which corresponds to the first selector switches of the Strowger systems. The B switch steps around its arms in obedience to impulses, each step taking five contacts, and each five contacts representing live trunks to the next order of switches. When the desired group is reached, the single impulse over the other side of the line shifts the energizing circuit, and the escapenient magnet comes into play, stepping the anus back one contact at a time until an idle trunk of the group is reached. it should be observed that the return movement is produced by the ordinary retract ing spring.

Having gotten down to the connector through these successive steps, this being the G switch shown in Figs. 9 and 1%, this only has one set of contacts, representing lines, there being no such thing as trunk groups, for if a line is busy that is the end of it. As party-line service is possible with this arrangement, and is also contemplated, it is necessary to provide means for permitting the last switch to come in on the calling partys own line if he wants another party on the same line. To this end I use a differential relay M for this purpose, which makes and breaks the private normal or busy line as the impulses come over one side of line, but is irresponsive to metallic circuit current.

line terminates in an A- where the meson i 'h batt ry anu s n thr 11gh tthe.c.i1;- Qu ts are from ground to both sides the line r-2 3 n t nti the all u scr be answers i alk ng. c r en vc back to the. ca g su s ri e y th sa s I .amal c "enabled to regulate the registering as shoyvn wherein the polar iged relay, Mi shown'jals o in Eigeal and 2,.

in Fig. 12, particularly,

controls the;.continuity of the meter trunk which may run through every switch circuit mlm he subscribcfls instrument, in Fig. 11,

Figt terminating finally n th w p 9' which comes .upon a contac which may be a olid bank, this beingconnectcd to i ter- 'rnpter, so that when thedesir d lineis s efl ed' andthe wanted subscriber has answered,

emin nt will flow beck tbloughthe relay- M,

throwing ve the same, lo ng the,

mg trunk, and starting the register of Fag. [1,

which is associated with llhe icalling ll)?- scrihers A switch, and: .cpntinuing to flint-he same and to register thereon during .thecom tinuance'of aconnection- The feeding back "of interrupted current clean through the line ofswitches enables me ,to regulate the regislfation, that is the speed ofregistering, aciording to the character of the line called. Interrupters of difierent irequencies are connectedto the interrupter contacts associated with -.difi'.erent classes of lines, whereby the j subscriber is charged according to the class of." line he calls, and it maybe he. is not chargedat all, if. the wanted party is a dead- ;.85

head. y

'-'The balance 05: the circuits will be better I understood'from' a statement of operation,

winding of the relay tracing one call in its progress through all the's witches. f v Y The operation of my system. is as follows'iReferring now to Fig. 11, the subscriber desiring to make a. call removes hisre'ceiver from the hook, closing the circnitnf the relay M by the iollowing-path: wire 1, normally closed contacts of the relay M, one Windingof the difierential rela Mi 12, wiper a 27 to gound, battery B, 14:,

15, 16, wiper at, 13, other winding of M normally closed contacts of the relay M, wire 2, through the subscriber.s station .to line wire 1. The relay M becoming energized attracts its armature,

is closing and opening the various circuits;

The circuitof the magnet M is completed by the following path: ground, Wiper a 22,

contacts 23 and .25, wires and 9. normally closed contacts of the magnet Ill-1, wlre 10,. 'inagnetiM fwire 11, battery B to ground.

The energizing of the magnet M causes it to operate orfvibrate, turning the spindle'a.

to which the wipers a", & a? a and a are rigidly fastened and] so causing thorn tomove overt-he various contactsuflit will be. seen that the magnet M will continue to vibrate its armature turn the splndle by met r i sh w-. t the G wit h in a ratchet arrangement so long as the circuit of the relay M is closed and Wiper a is connected to ground. After the relay M is energized, it is kept locked in that position by m (Fig. 12) and fails to get ground, the relay 3/ f will become denergized, open the circuit of the magnet 'M?, and thereby stopith e rotation of the spindle c. If, on the other hand, the contact we should be busy or grounded, the relay M would '.still'continue to hold up, closing the circuit of the magnet M and causing the spindle to make another step. After the spindle has made one step, the circuit. of the relay is closed by the following. path: battery B, 11, relay M, 70, contact m (Fig. 12), wiper a*,-wires 9, and 20, contacts 25 and 23, wire 22, Wiper a to busy trunk m toground. The relay M, becoming energized, attracts its armature disconnecting the .Wires 1 and 2 from 12 and 13 respectively. The relays M and M will continue energized and the magnet M continue to vibrate, turningthe shaft .or spindle until the wiper a say one free from ground, the relays M and I M become deenergized', disconnecting the nlagnet M causing the spindle to come to rest with its Various wipers resting on contacts leading to an idle first selector or B switch. The instant this-happens, the wires .1 and 2 are again connected to '12 and 13 re ,spectively. The contact m on which the .switch i'siarrested is now grounded or made busy bythe following path: m?, a 22, contacts23nnd 24 to ground. This ground is placed .011 the contact m soas to prevent another incoming call .toco'me in on thesamc first selector *switch' Itwill also be noticed that when the switch hasbeen operated the wiper a restson-the grounded contact m thus rendering it. busy fonoutgoing calls, that is to say, calls from-the G or connector switch, and that-it normally-rests on the contact wa connected to wire 70 to actuate relay M when this is the called line picked up'by a con-- nector switch.

The calling subscriber is now connected to an idle B or first selector switch. Referring now to Fig. 12. the circuit of the relay 1 4 is closed by the following path: ground, con-' tacts 24 and 23 of the relay M, 22, a m .34, 6 4:1, M*, 40. 54, 52, 51, battery B to ground.

relay M by the following path-2 contacts '11 and 72, 73, M8 51; to main battery B. The

The relay M becoming energized, --attr'acts- 125 30,- The trunk wire 29 is connected to the" trunk wire 28 is now connected to. onewind ingot the relay M by the following path;

3f impulses over N o. 1 side of the line, now operates the relay M which in turn closes the circuit of the ma net M causin the .the magnet .l\ The relay M, which was formerly kept energized through the Wiper g resting on a grounded contact, is now kept'energized by the following path: battery B, 97, M 113, 114, contacts 115 and 116, 117, contact's 118 and 119 of the relay- M, 120 to ground. Therefore, so long as the relay M itemainsnormal, the relay M? will be held or locked up'and the shaft can be stepped around as far as necessary.

After the, subscriber has sent in the third V set of impulses over No.1 side of the line, a 'momentary nnpulse 1s sent m over No. 2

side of the line operating the relay M which will in turn open the circuit of the relay M allowing it to assume its normal position cutting the lines through and leaving all the relays in their normalv positions. The: calling subscriber is'now connected to the contacts leading to the desired line. Suppose this line was busy. The contact m (Fig. 15) on which the wiper g rests would be grounded or busy and the circuit of the relay M would remain closed even though the magnet M is operated by the following path: ground, 9 121, 117, contacts 116 and 115, 114, 113,11, 97 to bat: tery B. It is evident that the relay M being kept energized, keeps the wires 98 and 100 respectively. disconnected from the wires 99 and 101, thus preventing the callingsubscriber listening in on a busy line.

Taking it for granted that the line called for is not busy, the relays M and M become' deenergized, the lines connected through and the contact m on which the wiper g rests, will be grounded by the following path: 121, 117, contacts 118,119, 12Q

to ground.

Referring now to Fig."15, the contact m being grounded closes the circuit of the relay M by the following path 122, a 123,

M 124 to battery B and ground. The relay M operating, clears the called subscribers individual line from any connection with its individual switch A. The;

calling subscriber now being connected straight through to the called subscriber, it only remains-necessary to supply generator 'current to the called line which is done automaticallv'by -means of the grounded interrupter Fig. 15 and the relay M 9, Fig. 14. The circuit of the magnet M is closedperiodically by the following path: ground,

disconnecting the calling subscrib r and connecting ringing current out to the called subscribers line, ringing the telephone intermittently until he answers or until the calling party hangs up. The relay'Mflis connected from main battery. toone of the trunk and the relay M5 is lconnected from ground to the other side of the trunk.

So, therefore, the called subseribe'fupon taking down his telephone, energizes both the relays M and 1P ,It will be noticed that the relayslfvf and M have their circuits open when the relay M operates. It will also be noticed that the relaysM and M? have their circuits normally open but'are closed as soon as the magnet M operates, Therefore, the called party in. removing his telephone and-operating 1W and M? cuts off the relays M and M and cuts onthe relays M and M and in this manner has supplied talking current back .to' the calling subscriber.

If, at. the

end of the conversation, the

called sulis'criber hangs upfirs't, it causes both sides of the line to be grounded'andthe circuits of the line side to be opened and those of the mate side to be closed.,, By the line side I mean No. 1 side of the line where the operating'inipulses are Sentimj'andby; the mate side'No. 2 side ofthe linewhere' the momentary or switching impulses are sent in. By this, ground being 'pla'cedlon, both sides at once, itwifll be'seen that the relay M becomes deenergized by being shuntechby' the ground at the subscriber-is station,- and'M remains energized closing the release circuit of the magnet M? which" is in series with M. The closingof the. two

wires together at the called,subscribers'station puts ground on wiper 9 completing the following circuit 2 g, wires99, 98, relay M to ground robbing, M of cui'rentwl ile M remains energized by current inthe fol lowing circuit: Viper 9 wires 101, 100, re-

lay M main battery B. Themom'enta 'ry energizing of M closes the circuit of release magnet M the'lat-ter being in series with the release relay M causes it to be energized which in turn energizes V M in series with M The latter then energizes M and M ni In this way-all the switches will be released successively in reverse direction iio to the-order in whichthey were operatedto establishrthe connection. The releasing of the connector switch has just been describedi" Thisis followed by therelease of aie'secon'a select, l s ay ifthelreof be g energized over the following circuit: batt 'ay I B, wire-105, contacts 0, 0 "',of lV w' "e contacts 0 o ofM w res"0. '0 l a 1 ai (Fig. 13), Wiper 0 wire 0 relayiM Wire o ,"contact'springs 0 .o,.-to gro H lease magnet M wires'o 0", contact ceiving current over the following pathz' hatter B wires 2 ma net M wire 7 7 7 3 I? 7 6 p contact springs 72*, p oi: M wires 22 -49, contact m", (Fig. 12) wiper 6 wires L2 and 43, relay M wire 44:, contact springs '17, 7 8, wire 7 9 to ground. Similarly M closes the circuit of release magnetfhi. of

' 33 wiper a Wire 21, release magnet M the first selector and M of the line switch of calhng subscriber, as will be seen by tracing the followlng circuits: ground, wire i 'Z 9, contact springs 37, 38 of relay M wires '36, 33 andi35, release magnet hi wires 54:, 52, 51,.battery B, ground. M receives cur rent over the following circuit: ground,

wire 7 9, contacts 3?, 38, wire 33, terminal Wire 14, battery B, ground. Therefore, when the relay M is disconnected, the entire set of switches is released and returned to their those of themate-sidh holding up M. This combination closes the release circuits and causes thensame operation just described over the last described circuits' Now sup-- posing that the called party did not answer or was husy, then both' sides of the line would he closed momentarily to ground at the calling suhscriheusstation, causing the relays M and M to pull up at the same time, whichcloses the release circuit and thereby reieases the switches in the same manner. The circuit of relays M and M may be traced as follows: ground ausubscrihers station, line and mate conductors Land- 2; through the several switches to wire 93 (Fig-14;) relay M wires 102, 105, to battery B: wire 100, relay M wire 106, contact 107, springs 13.6, 111, wires 112, 105 to battery B.

Havin thus described in" invention. what a Y ciaini and desire to secure by Letters Patout is:

1. In an automatic telephone system, the

combination with the suhscribers instruwith said terminals, electromagnetic oper ating mechanism for advancing said wipers adapted to respond to impulses of'current in the instrument circuits to move the wipers into engagement with one terminal of a given group, and arresting them in such positionand other operating devices automatically actuated when the switch connected to the selected terminal s husy to move said wipers within the group teimmais into mes -ii engagement with a terminal connected to an idle switch.

2. In an automatic telephone system, the combination with the subscribers instrument circuits having means for despatching impulses of current thereover and trunking and connector switches for interconnecting them, the trunkingswitches comprising terminals arranged in groups and the connector switches being tied to the separate terminals in said groups, of wipers cooperating with said terminals, electromagnetic, operating mechanism for" advancing said wipers adapted to respond to impulses of current in the instrument circuits to move the wipers into engagement with the last terminal of a given group and other devices for causing a retrograde movement of the wipers, which are actuated when the switch of said last group terminal is busy. I

3. In an automatic telephone system, the combination with subscribers instrument circuits having means for despatching impulses of current thereover and trunking and connector switches for interconnecting them, the trunking switches comprising terterminal of a given group in response to current impulses in the instrument circuits, and other mechanism controlling the subse quent movement of the wipers and adapted to cause them to engage each terminal in the selected group of terminals, said mechanism being normally inoperative and adapted to be actuated whenever the wipers engage a terminal connected to a busy switch.

4.111 an automatic telephone system, the combination with suhscribers instrument cir cuits having means for despatohing imthem, the trunking switches comprising terminals arranged in groups and the connector switches being tied to the separate terminals in said groups, of wipers cooperating with said terminals, mechanism for operating the wipers progressively, each movement advancing the wipers over complete groups of terminals, and into engagement with the last terminal of each group and other mechanism for operating the wipers retrogressively into engagement with the other terminals oi any group.

5. In an automatic telephone system, the combination with subscribers instrument circuits having means for despatching impulses of current thereover and trunking and connector switches for intercbnnecting them, the trunking switches comprising terminals arranged in groups and the connector switches being tied to the separate terminals insaid groups, 'of wipers cooperating with'said terminals, mechanism for operating the wipers progressivelyv in response to current impulses in the instrument circuits, each ad- Vance movement of the wipers carrying them over a complete group of terminals, and into engagement with the last terminal of each group and? other mechanism for operating the wipersretrogressively into enga'gement with the other terminals of any group, said lase -mentioned mechanism be ing normally inoperative but adapted to be actuated to cause retrogression of the wipers each time theyen'gage terminals of busy 16 I switches. v

6.. In an automatictelephone system, the combination with a plurality of normally open instrument circuits, a line switch for each circuit having a bank of terminals and wipers cciiperating therewith and forming part of the instrument circuits, ,a plurality of connector switches having terminals for the instrument circuits, and wipers cooperating therewith and trunk switches compris- 5 circuits connecting similar terminals of the line switches in multiple to the wipers of the trunk switches, sinnlar terminals of the trunk switches terminals being arranged in groups, of electromagnetic mechanism for operating the wipersor each line switch which 1s adapted to be actuated when its instrument circuit is closed to select a trunk circuit leadingto an idle trunk switch, electromagnetic devices under the vcontrol of the instrument circuits for causing the trunk switch wipers to move progressively over complctegroups of tero minals, other devices for operating them retrogressively .to engage terminals of an idle connector switch in the selected group, and.

mechanism alsc under the control ofv the instrument circuits for operating the wipers v of the connector switches. e a

' 7. In a telephone exchange system, a movable switch terminal, stationary'contacts arranged in groups traversed by said terminal, means for moving said terminal in one direction to select the desired group, and means for moving said terminalin a reverse direction to'select an individual contact in said group. 1

8. In a telephone exchange system, amovable switch member, stationary contacts arranged in groups traversed by saidterminal, meansffor moving said terminal in one, di-. 'rection to select and establish connection with the last terminal of a desired group if said terminal is idle, said terminal ingthereverse direction when the saidlast terminal is busy and to "confinue' such; retrograde movement until an idle terminal isiselected.

9.1a a telephone exchange system, the

terminals and cooperating wipers, trunkv trunk circuits connectto the wipers of the connector switches, said and means for moving combination with a selector apparatus havmg a movable contact member, contact terminals with which said member cooperates, v

means for imparting to said contact member a selective movement :past said contact terminals in one direction, and means for causing'a selective movement byfsaid con tact member in the opposite direction.

10. In a telephone exchange system, the

combination with a selector apparatus 'hav- -11. In a telephone exchange system the combination with a connecting circuit, of a selector comprising a movable brush carrier and banks of line terminals arranged in groups, driving means for moving said brush carrier in one direction, a sender device associated with said connecting circuit for controlling said driving means to move said brush 'carrier toselect a group of line terminals, electromagneticallycontrolled means for'rctaining said brush carrier in such selectmg position, and means for operatmg said retaining means to intermittently release said brush carrier and allow it to bemoved step-by-step until anidle line has been foun 12. In a telephone exchange system, thecombination with a connecting circuit, of a selector switch com rising a movable brush carrier and banks of line terminals arranged in groups, electromagnetically controlled means for moving said carrier, a sender associated with said connecting circuit'for controlling said means to move said brush carrier in one direction to select a group of terminals and e'lectromagneticallycontrolled means intermittently operated to cause said carrier to move in'the reverse direction to select a desired line in said group.

13. In a telephone exchange system, the combination with a connecting circuit, of a selector switch comprising a movable brush carrier and banks of line terminals arranged in. groups, electromagnetically controlled means for moving said carrier, a sender associated with said connecting circuit for controlling said means to move'said brush carrier in one direction to select a group of terminals, and electromagnetically controlled combination with a connecting circuit, of a selector switch comprising a movable brush carrler and banks of line terminals arranged in groups, driving means for said carrier, a sending device associated with said connecting circuit arranged to control said driving means to move said carrier to select a group of line terminals, eleotromagnetically controlled Ineans for retaining. said carrier in its displaced position, and means for operating said, retaining means to release said carrier step-by-step until an idle line has been found.

15. In a trunk line selector, a selecting magnet and circuit,-trunk line terminals, a movable terminal connected with calling line, selecting armature, means that move 

